The present invention relates to lead frames for semiconductor devices of the resin encapsulation type and more particularly, relates to frames that have frames formed at different levels of a surface of an outer frame and a surface positioned as an island, and where the lead frame is completely encapsulated by resin when resin encapsulation of the depressed portion is performed.
FIG. 1 is a view of a lead frame that is a part configuring a semiconductor device of the small-outline J-leaded package (SOJ) type, and for simplicity of description, the inner leads and their supporting portions have been omitted.
In FIGS. 1 and 1A, numerals 1 and 2 are outer frames, and these outer frames 1 and 2 are supported at constant intervals by inner lead bridge members that extend parallel and which are not shown in the figure.
The numeral 3 is an island, and the numerals 4 and 5 are island suspension leads. The island 3 is supported by the outer frames 1 and 2 via the island suspension leads 4 and 5.
These island suspension leads 4 and 5 are between the outer portion of each of the outer frames 1 and 2 of the island 3 and the respectively corresponding outer frames 1 and 2, and respectively bridge between the end portions on the side of the outer frame 2 of the island 3 and the outer frame 2, and the end portion of the outer fame 1 of the island and the outer frame 1.
The integrated circuit (IC) is, formed as described in the following, using a lead frame that has a configuration such as this.
First, a chip 6 is mounted on the island 3 and bonding is performed between the inner lead and the electrode of this chip 6.
Then, resin molding is used to perform resin encapsulation of the island 3, the chip 6 and the inner leads and the like. In the figure, numeral 7 is this resin encapsulation region.
After this, the island suspension leads 4 and 5 are cut and the distal end of the outer lead is separated from the lead frame, and forming of the outer leads is performed.
Finally, the island suspension leads 4 and 5 are separated from the outer frames 1 and 2 and a single IC is completed.
However, the island 3 is depressed with respect to the other portions of the lead frame, and the portions indicated by 4a and 5a in the island suspension leads 4, 5 is a curved portion that is the result of the formation of the depressions, that is, it is a distal end of a depression. This depression maintains a sufficient distance between the corner of the chip 6 and the bonding wire when bonding is performed, and prevents contact between the wire and the chip 6.
The bent portions (the depression end portions) 4a, 5a in these island suspension leads 4 and 5 are proved so as to be housed inside the resin encapsulation region 7. The reason for this is that having the bent portions 4a and 5a extending midway from the resin encapsulation region 7 means that they are sandwiched by the mold when molding is performed and this causes them to be deformed. A special mold is therefore required to prevent this.
However, along with the recent large sized chips it is not possible to sufficiently maintain the distance between the outer frames 1 and 2 and the island end portion 3 so that the bent portions 4a and 5a can be accommodated inside the resin encapsulation region 7, and there are occasions when a depression has to be omitted.
Along with the recent large-sized chips in conventional lead frames, there are therefore instances where it is not possible to sufficiently maintain the distance between the outer frames 1 and 2 and the island end portion 3 so that the bent portions 4a and 5a can be accommodated inside the resin encapsulation region 7.